South Africa have provisionally suspended Bjorn Basson and Chiliboy Ralepelle and sent them home from the squad's tour of Britain and Ireland after the pair tested positive for a banned substance on 6 November.
Basson, a 23-year-old winger, and Ralepelle, a 24-year-old hooker, were randomly tested after the 23-21 win over Ireland, with the results delivered on Sunday night showing traces of methylhexaneamine.
The two players, who are entitled to request that their 'B' samples are tested, are due to fly home later today.
South Africa coach Peter de Villiers is now investigating the rest of his squad and what supplements they are taking to ensure any problems are not widespread.
He told www.supersport.com: ‘We have done quite a bit already, we are busy sending stuff for testing. Obviously we have to look at what might have caused this and we don't want to put the players at risk.
‘If there is something that we are taking as a squad that might have caused this then we must find that out now.
‘When I informed the two players that they had been tested positive they were both extremely shocked and disappointed.
'The rest of the team were also gutted when they heard. I was informed of this at 2am on Monday morning, and now we must follow the correct processes as laid down by the International Rugby Board.’
Basson was already due to leave the tour because of an ankle injury suffered against Wales on Saturday, but the two players will now head home under different circumstances.
Basson won the third of his four caps in the win against Ireland and is the record holder for the most tries in a Currie Cup campaign.
Ralepelle is slightly more experienced than Basson, having picked up 17 caps, while he was also the first black player to captain the national side when he led them out against a World XV in Leicester.
The hooker plays his club rugby for the Blue Bulls and came off the bench in Saturday's win over Wales.
Basson started the game against Ireland, while Ralepelle was an unused substitute.
A statement from South Africa Rugby Union released on Monday afternoon read: ‘Six Nations Rugby Ltd - who administer the November internationals - informed the South African Rugby Union of the positive Tests on Sunday evening.
‘As a result the pair are provisionally suspended from all rugby and will return to South Africa on Monday. Basson injured an ankle in Saturday's win over Wales and was due to return anyway.
‘The players were randomly drawn for testing by anti-doping officials following the Test at the Aviva Stadium. The players have the right to request that their 'B' sample be tested.
‘The pair returned an adverse analytical finding for methylhexaneamine, a 'non-specified stimulant' on the prohibited substances list of the World Anti-Doping Agency (WADA). It is
scheduled to be re-classified as a "specified stimulant" from 1 January 2011.’
